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cbd4eb5717
This patch currently only applies to the "ubuntu-cpc" project.
More and more logic has been going into the hook scripts to decide under which conditions they should run or not. As we are moving to parallelized builds of image sets, this will get even more complicated. Base hooks will have to know which image sets they belong to and modification of the dependency chain between scripts will become more complicated and prone to errors, as the number of image sets grows.
This patch introduces explicit ordering and dependency handling for scripts through the use of `series` files and an explicit syntax for dependency specification.
69 lines
2.9 KiB
Markdown
69 lines
2.9 KiB
Markdown
# TL;DR
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In order to generate the hooks for a specific image target set, call the
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`make-hooks` script, located in `hooks.d` as
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./make-hooks --hooks-dir ../hooks <image_set>
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where `image_set` is the name of a series file (e.g. "vagrant") without leading
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path components. Do *not* check in the `hooks` folder, it is automatically
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generated by `auto/config` during Live Build runs.
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# Hook placement and ordering
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Scripts live in subfolders below the `hooks.d` folder. Currently the folders
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`chroot` and `base` exist. The folder with the name `extra` is reserved for
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private scripts, which are not included in the source of livecd-rootfs. The
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scripts are not numbered, instead the order of their execution depends on the
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order in which they are listed in a *series* file.
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Series files are placed in subfolders `hooks.d/base/series` or
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`hooks.d/extra/series`. Each series file contains a list of scripts to be
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executed. Empty lines and lines starting with a `#` are ignored.
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Series files in `extra/series` override files in `base/series` with the same
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name. For example, if a series file `base/series/cloudA` exists and a series
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file `extra/series/cloudA`, then the latter will be preferred.
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A series file in `extra/series` may also list scripts that are located in the
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`chroot` and `base` folders. In addition, series files can *depend* on other
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series files. For example, the series files for most custom images look similar
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to this:
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depends disk-image
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depends extra-settings
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extra/cloudB.binary
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Where `disk-image` and `extra-settings` may list scripts and dependencies which
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are to be processed before the script `extra/cloudB.binary` is called.
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ACHTUNG: live build runs scripts with the suffix ".chroot" in a batch separate
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from scripts ending in ".binary". Even if you arrange them interleaved in your
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series files, the chroot scripts will be run before the binary scripts.
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# Image set selection for Live Build
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During a Live Build, enumerated symbolic links are generated based on the
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contents of one or more series files. The series files are selected according
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to the contents of the `IMAGE_TARGETS` environment variable. For example, in
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order to trigger the build of `squashfs` and `vagrant`, list them in the
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`IMAGE_TARGETS` variable as `squashfs,vagrant`. The separator can be a comma,
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a semi-colon or whitespace.
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The generation of the symbolic links is triggered from the `auto/config` script,
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from where the contents of the `IMAGE_TARGETS` environment variable are passed
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on to the `make-hooks` script.
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# Symlink generation
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Since Live Build itself does not know about series files, a traditional `hooks`
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folder is generated using the `make-hooks` script. The script takes as arguments
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the names of the series files to be processed.
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The script parses the series files and generates enumerated symbolic links for
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all entries. Per default, these are placed into a directory named `hooks` next
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to the `hooks.d` directory. This can be changed using the `--hooks-dir`
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parameter.
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